1. Field of the Invention
The present invention relates to an implantable heart monitoring device which is able to detect vibrations in order to obtain information concerning the heart.
The invention also relates to a system including such a device and to the use of the system. The device may be used to monitor the status of a heart of a human or animal being as well as to stimulate said heart.
2. Description of the Prior Art
Several different implantable devices for monitoring and stimulating a heart are known.
U.S. Pat. No. 6,044,299 describes an implantable medical device that has a housing containing an accelerometer which detects vibrations of the housing. The accelerometer generates a signal in response to the detected vibrations, which is supplied to a signal processing unit. The signal processing unit generates, for each of a number of pre-determined frequency ranges, a parameter value indicative of a defined attribute of the signal. The signal processing unit forms a ratio between any two of these parameter values, and emits at least one status value dependent on this ratio. The status value is uniquely indicative of a predetermined type or level of cardiac activity, and the status values can be used as a control signal for controlling therapy, such as cardiac stimulation, administered by the implantable medical device.
United States Patent Application Publication 2005/0027323 describes a device for monitoring cardiac blood pressure and chamber dimension. The dimension sensor or sensors comprise at least a first sonomicrometer piezoelectric crystal mounted to a first lead body implanted into or in relation to one heart chamber that operates as an ultrasound transmitter when a drive signal is applied to it and at least one second sonomicrometer crystal mounted to a second lead body implanted into or in relation to a second heart chamber that operates as an ultrasound receiver. The time delay between the generation of the transmitted ultrasound signal and the reception of the ultrasound wave varies as a function of distance between the ultrasound transmitter and receiver which in turn varies with contraction and expansion of a heart chamber between the first and second sonomicrometer crystals.
U.S. Pat. No. 4,771,792 describes a non-invasive system and method for inducing vibrations in a selected element of the human body and detecting the nature of responses for determining mechanical characteristics of the element. In particular an internal pressure of the selected body element is determined.